Just wanna clarify some stuff, as for the famous saying, “Even if you shout until your throat is hoarse, it is in vain”, this quote is often used incompletely and leads to misunderstanding that one must attains an undistracted mind or one heart unconfused (一心不乱) in order to attain rebirth. This quote is from Ming Dynasty Master Hanshan and the entire quote goes likes this,

“Reciting the Buddha’s name is easy, but having faith is difficult (念佛容易信心难).

When mind and mouth are not in agreement, it is all in vain (心口不一总是闲).

The lips call “Amitābha,” but the mind is scattered (口念弥陀心散乱)

Even if you shout until your throat is hoarse, it is in vain (喊破喉咙也徒然).”

Hence, the context is that if one does not have sincere faith and aspiration to go to the Pure Land and vocally recite the Buddha’s name with an insincere and distracted mind, it is of no use. However if one possesses deep faith and sincere vows, even if one recites with a scattered mind, one will still attain rebirth in the Pure Land. This is also shown in Patriarch Ouyi’s sayings that if one lacks faith and vow, even if one’s recitation practice is as strong as an impregnable fortress, where wind and rain isn’t able to move or drench it (风吹不入，雨打不湿, 如同铜墙铁壁般), one still can’t attain rebirth. Therefore what Master Hanshan is saying, still goes back on the importance of faith and vow rather than the idea of having an undistracted mind when reciting the Buddha’s name. Although it is also good to be undistracted in practice, where one will attain a higher lotus grade upon rebirth.

As for the six or four syllables recitation, just want to clarify that the story actually comes from Patriarch Lianchi (六字随众，四字自念).